Lithographic Apparatus and Device Manufacturing Method Utilizing a Substrate Handler

ABSTRACT

A substrate handler is provided. The substrate handler includes a support surface configured to carry a substrate and a pre-conditioning unit configured to pre-condition the substrate. The substrate handler is configured to move the substrate relative to a substrate table.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.11/320,494, filed Dec. 29, 2005 (now allowed), which is acontinuation-in-part of U.S. application Ser. No. 11/157,201, filed Jun.21, 2005, (now U.S. Pat. No. 7,538,857), which claims benefit under 35U.S.C. §119(e) to U.S. Provisional Application No. 60/639,960, filedDec. 30, 2004, which are all incorporated by reference herein in theirentireties.

U.S. application Ser. No. 11/157,201 is also a continuation-in-part ofU.S. application Ser. No. 11/067,671, filed Mar. 1, 2005, (now U.S. Pat.No. 7,242,458), which claimed benefit under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 60/638,171, filed Dec. 23, 2004,which are all incorporated herein by reference in their entireties.

BACKGROUND

1. Field of the Present Invention

The present invention relates to a substrate handler and methods ofusing same. The present invention extends to device manufacturingmethods using a lithographic apparatus which in part comprises thesubstrate handler.

2. Related Art

A lithographic apparatus is a machine that applies a desired patternonto a target portion of a substrate. Lithographic apparatus can beused, for example, in the manufacture of integrated circuits (ICs), flatpanel displays (FPDs) and other devices involving fine structures. In aembodiment of the present invention lithographic apparatus, a patterningmeans, which is alternatively referred to as a mask or a reticle, can beused to generate a circuit pattern corresponding to an individual layerof the IC (or other device), and this pattern can be imaged onto atarget portion (e.g., comprising part of, one or several dies) on asubstrate (e.g., a silicon wafer or glass plate) that has a layer ofradiation-sensitive material (resist). Instead of a mask, the patterningmeans can comprise an array of individually controllable elements, whichserve to generate the circuit pattern.

In general, a single substrate will contain a network of adjacent targetportions that are successively exposed. The substrate is secured on asubstrate exposure table or stage, during a scanning process. Knownlithographic apparatus include so-called steppers, in which each targetportion is irradiated by exposing an entire pattern onto the targetportion in one go, and so-called scanners, in which each target portionis irradiated by scanning the pattern through the projection beam in agiven direction (the “scanning”-direction) while synchronously scanningthe substrate parallel or anti-parallel to this direction.

Substrates that are to be irradiated on the substrate exposure table arestored in a substrate storage area or track, and are then moved by arobot or a conveyor to a substrate handler. The substrate handler isadjacent the substrate exposure stage and is used to transfer asubstrate directly to and from the exposure table. Known substratehandlers are capable of handling only one substrate at the same time.However, such substrate handlers that are capable of handling only onesubstrate at any one time have the disadvantage of only being able topick up and/or put away substrates, i.e., the substrate handler can putan exposed substrate away before it can pick up and load an unexposedsubstrate. During these handling movements, the parts of thelithographic apparatus involved with irradiating substrates, are sittingidle. In addition, the time necessary for these movements by thesubstrate handler depends on the layout of the lithographic apparatus,and the demands of the user, and so is difficult to control. Hence, amajor problem with known substrate handlers is that the throughput of asingle stage machine (such as FPD machines) suffers on account of thedelays associated with the handling time of the substrates.

A further problem associated with known lithographic apparatus is thatthe handling stage of the apparatus consisting of the substrate handleris located next to the exposure table. This gives the apparatus a“footprint” penalty, i.e., the total floor area occupied by theapparatus is large. A problem with having a large footprint is that theapparatus can be contained within a large frame structure that requiresmany cover plates, and requires a complicated network of wiring. Thisresults in high manufacturing costs, which in turn increases the cost ofthe final product. In addition, the total weight of the apparatus ishigh, and is therefore difficult to move about.

Therefore, what is needed is an apparatus and method using a substratehandler which can function more efficiently. What is also needed is amethod of manipulating substrates in a lithographic apparatus.

SUMMARY

According to a first embodiment of the present invention, there isprovided substrate handler. The substrate handler includes a supportsurface configured to carry a substrate and a pre-conditioning unitconfigured to pre-condition the substrate. The substrate handler isconfigured to move the substrate relative to a substrate table.

Table 1 below shows a comparison of the handling sequence of aconventional single substrate handler, and a substrate handler accordingto the present invention, i.e., one adapted to carry a plurality ofsubstrates simultaneously.

TABLE 1 A single substrate handler A double substrate handler 1. Pick upexposed substrate 1. Pick up exposed substrate from substrate table fromsubstrate table 2. Move exposed substrate to take- 2. Move handler overstage, where it is stored 3. Put exposed substrate on take- 3. Putunexposed substrate on over stage substrate table 4. Move to pick-uptable where unexposed substrates are stored 5. Pick up an unexposedsubstrate 6. Move to substrate table 7. Put unexposed substrate onsubstrate table

Hence, the throughput using the lithographic apparatus according to thepresent invention increases because of the fast substrate-swapping timeon and off the substrate table, which is made possible by the substratehandler. The substrate handler can be adapted to move in the verticaldirection relative to the exposure table. The length of travel in thevertical direction is significantly less than the horizontal traveldistance of conventional handlers and so further throughput improvementsare achieved.

In another embodiment, a lithographic apparatus is provided. Thelithographic apparatus includes a base plate, a substrate tableconfigured to support a substrate, a patterning system configured toprovide a pattern to a target portion of the substrate, and a substratehandler configured to move the substrate relative to the substratetable. The substrate handler is positioned substantially over the baseplate. The base plate is configured to support the substrate table.

In still another embodiment, a method is provided. The method includesmoving a substrate handler so that a first support surface issubstantially aligned in a horizontal plane with a substrate table,loading a substrate directly from the first support surface of thesubstrate handler onto the substrate table, patterning a substrate usingthe patterning system, unloading the exposed substrate from thesubstrate table onto a second support surface of the substrate handler,and removing the exposed substrate from the second support surface ofthe substrate handler.

In another embodiment, a method is provided. The method includesreceiving a substrate on a substrate table supported by a base plate,patterning a target portion of the substrate, and moving the substraterelative to the substrate table using a substrate handler. The substratehandler is positioned substantially over the base plate.

In another embodiment, a lithographic apparatus is provided. Thelithographic apparatus includes a substrate table configured to supporta substrate, a patterning system configured to provide a pattern to atarget portion of the substrate, and a substrate handler configured tomove the substrate relative to the substrate table. The substrate tableis supported on a base plate and traveling therealong during a scanningoperation between a start position and an end position. The substratehandler includes a loading platform disposed on one side of thesubstrate table above the base plate, and an unloading platform disposedon an opposite side of the substrate table and to one side of the baseplate, at least the loading platform being vertically movable between araised position above the substrate table and a lowered position inwhich the unloading platform is substantially aligned in a horizontalplane with the substrate table. The loading platform is configured toload the substrate onto the table if the loading platform is in thelowered position, and to receive the substrate from the substrate tableif the loading platform is at an end position after the scanningoperation. Both the loading and the unloading platform are substantiallylevel with the substrate table when the substrate table is at the endposition so that loading and unloading is configured to be performedsubstantially simultaneously.

In another embodiment, a substrate handler is provided. The substratehandler includes a substrate table configured to support a substrateduring exposure to a beam of radiation and a plurality of platforms.Each platform is configured to carry the substrate. The substratehandler is configured to load the substrate onto the substrate tablebefore exposure and to unload the substrate from the substrate tableafter exposure.

Further embodiments, features, and advantages of the present inventions,as well as the structure and operation of the various embodiments of thepresent invention, are described in detail below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form a partof the specification, illustrate one or more embodiments of the presentinvention and, together with the description, further serve to explainthe principles of the invention and to enable a person skilled in thepertinent art to make and use the invention.

FIG. 1 shows a schematic side view of a lithographic apparatus,according to one embodiment of the present invention.

FIG. 2 shows an enlarged perspective view of a first embodiment of thepresent invention showing a substrate handler, substrate exposure stage,and robot.

FIG. 3 a-g shows a schematic side view representation of the sequence ofloading and unloading a substrate on to the substrate exposure stageusing one embodiment of the present invention.

FIGS. 4, 5, and 6 show enlarged perspective views, according to variousembodiments of the present invention.

FIGS. 7, 8, and 8 a show various perspective views of a substratehandler, according to various embodiments of the present invention.

FIGS. 9 a-h and 10 a-h show a schematic side view representation of a“Front in, Front out” loading sequence, according to various embodimentsof the present invention.

FIGS. 11, 12 a-h, 13 a, and 13 b show various side view representationsof “Front in, Rear out” loading concepts, according to variousembodiments of the present invention.

FIGS. 14 a, 14 b, and 14 c show schematic plan and side views showing afootprint between first and second lithographic apparatus, according toone embodiment of the present invention.

FIGS. 15 a and 15 b show schematic side views of one embodiment of thepresent invention during substrate exposure.

FIGS. 16 a, 16 b, 17 a, 17 b, 17 c, and 17 d show schematic side viewsof various embodiments of the present invention during pre-conditioningand substrate exchange.

FIGS. 18 a, 18 b, and 18 c are diagrammatic plan views of severalalternative embodiments of the lithographic apparatus of the presentinvention.

FIG. 19 is an alternative embodiment of a substrate handler inaccordance with the present invention.

DETAILED DESCRIPTION Overview and Terminology

The term “patterning system” used herein should be broadly interpretedas including any device that can be used to impart a radiation beam witha pattern in its cross-section such as to create a pattern in a targetportion of the substrate. It should be noted that the pattern impartedto the radiation beam may not exactly correspond to the desired patternin the target portion of the substrate, for example if the patternincludes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit. The patterning system can alsobe an imprint template, or other suitable mean of applying a pattern toa substrate.

The patterning device can be transmissive or reflective. Examples ofpatterning devices include masks, or an array of individuallycontrollable elements. Masks are well known in lithography, and includemask types such as binary, alternating phase-shift, and attenuatedphase-shift, as well as various hybrid mask types.

The term “array of individually controllable elements” as here employedshould be broadly interpreted as referring to any means that can be usedto endow an incoming radiation beam with a patterned cross-section, sothat a desired pattern can be created in a target portion of thesubstrate. The terms “light valve” and “Spatial Light Modulator” (SLM)can also be used in this context.

Examples of such patterning means include the following.

A programmable mirror array. This can comprise a matrix-addressablesurface having a viscoelastic control layer and a reflective surface.The basic principle behind such an apparatus is that (for example)addressed areas of the reflective surface reflect incident light asdiffracted light, whereas unaddressed areas reflect incident light asundiffracted light. Using an appropriate spatial filter, theundiffracted light can be filtered out of the reflected beam, leavingonly the diffracted light to reach the substrate. In this manner, thebeam becomes patterned according to the addressing pattern of thematrix-addressable surface. It will be appreciated that, as analternative, the filter can filter out the diffracted light, leaving theundiffracted light to reach the substrate. An array of diffractiveoptical MEMS devices can also be used in a corresponding manner. Eachdiffractive optical MEMS device comprises a plurality of reflectiveribbons that can be deformed relative to one another to form a gratingthat reflects incident light as diffracted light. A further alternativeembodiment of a programmable mirror array employs a matrix arrangementof tiny mirrors, each of which can be individually tilted about an axisby applying a suitable localized electric field, or by employingpiezoelectric actuation means. Once again, the mirrors arematrix-addressable, such that addressed mirrors will reflect an incomingradiation beam in a different direction to unaddressed mirrors; in thismanner, the reflected beam is patterned according to the addressingpattern of the matrix-addressable mirrors. The required matrixaddressing can be performed using suitable electronic means. In both ofthe situations described hereabove, the array of individuallycontrollable elements can comprise one or more programmable mirrorarrays. More information on mirror arrays as here referred to can begleaned, for example, from U.S. Pat. No. 5,296,891 and U.S. Pat. No.5,523,193, and PCT patent applications WO 98/38597 and WO 98/33096,which are incorporated herein by reference.

A programmable LCD array. An example of such a construction is given inU.S. Pat. No. 5,229,872, which is incorporated herein by reference.

It should be appreciated that where pre-biasing of features, opticalproximity correction features, phase variation techniques and multipleexposure techniques are used, for example, the pattern “displayed” onthe array of individually controllable elements can differ substantiallyfrom the pattern eventually transferred to a layer of or on thesubstrate.

Although specific reference can be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein can haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat panel displays, thin-film magnetic heads, etc. The skilled artisanwill appreciate that, in the context of such alternative applications,any use of the terms “wafer” or “die” herein can be considered assynonymous with the more general terms “substrate” or “target portion”,respectively.

The substrate referred to herein can be processed or pre-conditioned,before or after exposure, in for example a track (a tool that typicallyapplies a layer of resist to a substrate and develops the exposedresist) or a metrology or inspection tool. Where applicable, thedisclosure herein can be applied to such and other substrate processingtools. Further, the substrate can be processed more than once, forexample in order to create a multi-layer IC, so that the term substrateused herein can also refer to a substrate that already contains multipleprocessed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.,having a wavelength of 365, 355, 248, 193, 157 or 126 nm) and extremeultra-violet (EUV) radiation (e.g., having a wavelength in the range of5-20 nm), as well as particle beams, such as ion beams or electronbeams.

The term “projection system” used herein should be broadly interpretedas encompassing various types of projection system, including refractiveoptical systems, reflective optical systems, and catadioptric opticalsystems, as appropriate for example for the exposure radiation beingused, or for other factors such as the use of an immersion fluid or theuse of a vacuum. Any use of the term “lens” herein can be considered assynonymous with the more general term “projection system”.

The illumination system can also encompass various types of opticalcomponents, including refractive, reflective, and catadioptric opticalcomponents for directing, shaping, or controlling the projection beam ofradiation, and such components can also be referred to below,collectively or singularly, as a “lens”.

The lithographic apparatus can also be of a type wherein the substrateis immersed in a liquid having a relatively high refractive index, e.g.,water, so as to fill a space between the final element of the projectionsystem and the substrate. Immersion liquids can also be applied to otherspaces in the lithographic apparatus, for example, between the mask andthe first element of the projection system. Immersion techniques arewell known in the art for increasing the numerical aperture ofprojection systems.

Exemplary Systems and Methods

FIG. 1 schematically depicts a lithographic projection apparatusaccording to a particular embodiment of the present invention. Theapparatus comprises an illumination system, an array of individuallycontrollable elements PPM, a substrate table (e.g., a wafer table) WT,and a projection system (“lens”) PL.

The illumination system (illuminator) IL provides a projection beam PBof radiation (e.g., UV radiation).

The array of individually controllable elements PPM (e.g., aprogrammable mirror array) applies a pattern to the projection beam. Ingeneral, the position of the array of individually controllable elementswill be fixed relative to item PL. However, it can instead be connectedto a positioning means for accurately positioning it with respect toitem PL.

The substrate table (e.g., a wafer table) WT supports a substrate (e.g.,a resist-coated wafer) W, and is connected to positioning means PW foraccurately positioning the substrate with respect to item PL. The tableWT is moveable on a base plate BP.

The projection system (“lens”) PL images a pattern imparted to theprojection beam PB by the array of individually controllable elementsPPM onto a target portion C (e.g., comprising one or more dies) of thesubstrate W. The projection system can image the array of individuallycontrollable elements onto the substrate. Alternatively, the projectionsystem can image secondary sources for which the elements of the arrayof individually controllable elements act as shutters; the projectionsystem can also comprise a micro lens array (known as an MLA), e.g., toform the secondary sources and to image microspots onto the substrate.

As here depicted, the apparatus is of a reflective type (i.e., has areflective array of individually controllable elements). However, ingeneral, it can also be of a transmissive type, for example (i.e., witha transmissive array of individually controllable elements).

The illuminator IL receives a beam of radiation from a radiation sourceSO. The source and the lithographic apparatus can be separate entities,for example when the source is an excimer laser. In such cases, thesource is not considered to form part of the lithographic apparatus andthe radiation beam is passed from the source SO to the illuminator ILwith the aid of a beam delivery system BD comprising for examplesuitable directing mirrors and/or a beam expander. In other cases thesource can be integral part of the apparatus, for example when thesource is a mercury lamp. The source SO and the illuminator IL, togetherwith the beam delivery system BD if required, can be referred to as aradiation system.

The illuminator IL can comprise adjusting means AM for adjusting theangular intensity distribution of the beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator ILgenerally comprises various other components, such as an integrator INand a condenser CO. The illuminator provides a conditioned beam ofradiation, referred to as the projection beam PB, having a desireduniformity and intensity distribution in its cross-section.

The projection beam PB subsequently intercepts the array of individuallycontrollable elements PPM. Having been reflected by the array ofindividually controllable elements PPM, the projection beam PB passesthrough the projection system PL, which focuses the projection beam PBonto a target portion C of the substrate W. With the aid of thepositioning means PW (and interferometric measuring means IF), thesubstrate table WT can be moved accurately, e.g., so as to positiondifferent target portions C in the path of the projection beam PB. Whereused, the positioning means for the array of individually controllableelements can be used to accurately correct the position of the array ofindividually controllable elements PPM with respect to the path of theprojection beam PB, e.g., during a scan. In general, movement of theobject table WT is realized with the aid of a long-stroke module (coarsepositioning) and a short-stroke module (fine positioning), which are notexplicitly depicted in FIG. 1. A similar system can also be used toposition the array of individually controllable elements. It will beappreciated that the projection beam can alternatively/additionally bemoveable while the object table and/or the array of individuallycontrollable elements can have a fixed position to provide the requiredrelative movement. As a further alternative, that can be especiallyapplicable in the manufacture of flat panel displays, the position ofthe substrate table and the projection system can be fixed and thesubstrate can be arranged to be moved relative to the substrate table.For example, the substrate table can be provided with a system forscanning the substrate across it at a substantially constant velocity.

Although the lithography apparatus according to the present invention isherein described as being for exposing a resist on a substrate, it willbe appreciated that the present invention is not limited to this use andthe apparatus can be used to project a patterned projection beam for usein resistless lithography.

The depicted apparatus can be used in various modes:

1. Step mode: the array of individually controllable elements imparts anentire pattern to the projection beam, which is projected onto a targetportion C in one go (i.e., a single static exposure). The substratetable WT is then shifted in the X and/or Y direction so that a differenttarget portion C can be exposed. In step mode, the maximum size of theexposure field limits the size of the target portion C imaged in asingle static exposure.

2. Scan mode: the array of individually controllable elements is movablein a given direction (the so-called “scan direction”, e.g., the Ydirection) with a speed v, so that the projection beam PB is caused toscan over the array of individually controllable elements; concurrently,the substrate table WT is simultaneously moved in the same or oppositedirection at a speed V=Mv, in which M is the magnification of the lensPL. In scan mode, the maximum size of the exposure field limits thewidth (in the non-scanning direction) of the target portion in a singledynamic exposure, whereas the length of the scanning motion determinesthe height (in the scanning direction) of the target portion.

3. Pulse mode: the array of individually controllable elements is keptessentially stationary and the entire pattern is projected onto a targetportion C of the substrate using a pulsed radiation source. Thesubstrate table WT is moved with an essentially constant speed such thatthe projection beam PB is caused to scan a line across the substrate W.The pattern on the array of individually controllable elements isupdated as required between pulses of the radiation system and thepulses are timed such that successive target portions C are exposed atthe required locations on the substrate. Consequently, the projectionbeam can scan across the substrate W to expose the complete pattern fora strip of the substrate. The process is repeated until the completesubstrate has been exposed line by line.

4. Continuous scan mode: essentially the same as pulse mode except thata substantially constant radiation source is used and the pattern on thearray of individually controllable elements is updated as the projectionbeam scans across the substrate and exposes it.

Combinations and/or variations on the above described modes of use orentirely different modes of use can also be employed.

Although the lithographic apparatus illustrated in FIG. 1 is an opticalapparatus, it will be appreciated that other non-optical patterningsystem can also be used to apply a pattern to a substrate. For example,an imprint lithography template can be used to imprint a pattern onto asubstrate. Thus, the term lithographic apparatus is not intended to belimited to an optical lithographic apparatus.

Referring to FIG. 2, there is shown one embodiment of the presentinvention. In particular, FIG. 2 shows parts of the apparatus 2 that areinvolved with moving and manipulating substrates 8 (referred to as W inFIG. 1) to and from a substrate exposure table 6 (referred to as WT inFIG. 1), on which the substrates 8 are supported during exposure by theillumination source PL. Adjacent the substrate table 6, there isprovided a substrate handler 12 for carrying substrates 8 to and fromthe exposure table 6. The substrate handler 12 has an upper stage 14 anda lower stage 16, both of which are suitably sized to accommodate asubstrate 8. The substrate handler 12 is referred to as a doublesubstrate handler 12 as it is able to support two substrates 8. Thesubstrate handler 12 is arranged to move upwardly and downwardly asindicated by arrow A-A in FIG. 1, so that either the upper or lowerstages 14,16 can be aligned in a horizontal plane with the substratetable 6.

The apparatus 2 includes a robot 10 for loading unexposed substrates 8on to the substrate handler 12, and also for unloading exposedsubstrates 8 from the substrate handler 12 after exposure on thesubstrate table 6. Both the upper and lower stages 14,16 of thesubstrate handler 12 are provided with a series of rollers 20, whichfacilitate loading and unloading of a substrate 8 therefrom. In theapparatus shown in FIG. 2, the upper and lower stages 14,16 are fittedwith four spaced apart rollers 20, each powered by a motor, although itis to be understood that other arrangements can be used such as, forexample, a conveyor belt, an air cushion or film on which the substratecan “float,” at least one linear actuator or a gripper mechanism forgripping a side edge of the substrate. The air cushion or film can beformed by providing the stages 14, 16 with a plurality of apertures (notshown) arranged to output a gas. The air cushion or film can be combinedwith a substrate table that has a surface of spaced raised regions suchas pimples or the like. This is known in the art as a burl table.

The substrate handler 12 is either positioned above, or is integratedwith, a pre-conditioning unit 18. The pre-conditioning unit 18 is usedto bring the temperature of the substrates 8 in the lower stage 16 afterthey have been coated with resists to the appropriate level prior to itsexposure on the substrate table 6. This is important so that thegeometry of the substrate can be carefully controlled during theprinting process. The pre-conditioning unit 18 comprises, for example,an aluminum conduction plate 19, which has a series of internalchannels. Water, which can be maintained at a temperature of about 23°C., flows along the channels and cools/heats the substrate 8 with whichit is in thermal contact. The cooled/heated (pre-conditioned) substrate8 can then be moved on to the table 6 for exposure. As an alternative tomaintaining the water at a constant temperature it can instead becontrollably variable so as to control the temperature of the substrate.

In order to bring the substrate close to the pre-conditioning unit 18,the stages 14 and 16 are collapsible so as to reduce the verticalspacing between them and the pre-conditioning unit 18. The surface ofthe pre-conditioning unit has a plurality of spaced grooves 22 that aredesigned to receive the rollers 20 of the lower stage 16 when thesubstrate handler is in a collapsed configuration.

Although the figures show the pre-conditioning unit 18 adjacent to thelower stage 16 it is to be appreciated that it could equally be disposedadjacent to the upper stage 14 so as to pre-condition an unexposedsubstrate disposed thereon.

Referring to FIG. 3, there is shown the sequence of loading/unloadingsubstrates 8 to and from the substrate exposure table 6 via the doublesubstrate handler 12, according to one embodiment of the presentinvention. In FIG. 3, an exposed substrate 8 is represented as 8 a, andan unexposed substrate is represented as 8 b. At stage (a), a firstunexposed substrate 8 b is shown in position on the robot 10, havingbeen picked up from a storage area (not shown) of unexposed substrates 8b. A second unexposed substrate 8 b is shown on the lower stage 16 ofthe substrate handler 12, and an exposed substrate 8 a is shown on thesubstrate exposure table 6. The upper stage 14 of the substrate handler12, which is currently empty, is positioned so that it is horizontallyaligned with the exposure table 6.

At stage (b), following exposure, the exposed substrate 8 a is moved offthe table 6 and on to the upper stage 14 of the substrate handler 12, ina direction as indicated by arrow B. Rollers 20 on the upper stage 14facilitate transfer of the substrate 8 a on to the substrate handler 12.

At stage (c), the substrate handler 12 is moved upwardly in a directionindicated by arrow C, so that the lower stage 16, and hence, unexposedsubstrate 8 b thereon, is in horizontal alignment with the exposuretable 6.

At stage (d), the unexposed substrate 8 b is moved in a directionindicated by arrow D off the lower stage 16 and on to the exposure table6. Rollers 20 on the lower stage facilitate transfer of the substrate 8b off the substrate handler 12.

At stage (e), the substrate handler 12 is moved downwardly in adirection as indicated by arrow E, so that the lower stage 16 is inhorizontal alignment with the robot 10.

At stage (f), the unexposed substrate 8 b on the robot 10 is moved in adirection as indicated by arrow F on to the lower stage 16 of thesubstrate handler 12.

At stage (g) of the sequence, the robot 10 is moved upwardly so that itis in horizontal alignment with the upper stage 14 of the substratehandler 12. The exposed substrate 8 a can then be moved off thesubstrate handler 12 in a direction indicated by arrow G on to the robot10. The robot 10 then moves the exposed substrate 8 a away from thesubstrate handler 12 to a storage area (not shown). The sequence is thenrepeated.

In one example, the substrate handler 12 could be fixed in a verticalposition, and it is the substrate table 6 that is moved vertically andrelative thereto.

Referring to FIG. 4, there is shown a double substrate handler 24,according to an alternative embodiment of the present invention. In thisembodiment, the double substrate handler 24 is integrated with the robot10. The double substrate handler 24 is attached to the top of the robot10 and comprises upper and lowers stages 14,16 as previously described.The Figure shows a substrate 8 on both the stages 14,16 of the doublesubstrate handler 24. In addition, the double substrate handler 24includes a pre-conditioning unit 18 attached to one side of the lowerstage 16 for pre-conditioning unexposed substrates 8 b prior to exposureon the substrate table 6. Again, it is to be appreciated that thepre-conditioning unit 18 can alternatively be associated with the upperstage 14 if unexposed substrates are loaded thereon.

Referring to FIG. 5, there is shown a double substrate handler 26,according to a further embodiment of the present invention. The doublesubstrate handler 26 has an upper and lower stage 14,16, each having twospaced apart elongate slots 25 extending along a plane thereof. The twoslots 25 in the upper stage 14 extend at 90° with respect to the twoslots 25 in the lower stage 16. Each of the slots 25 is designed toreceive, in sliding engagement, an elongate rod 27 of a transportdevice. The rods 27 are thus received in the stages 14 or 16 under thesubstrates and can be used to lift them free of the stage surface and totransport them to the exposure table. Similarly such rods 27 can be usedto transport unexposed substrates from a conveyor belt or track on tothe handler 26.

Both stages 14,16 of the double substrate handler 26 include partiallysunken rollers 20, which are provided to facilitate the movement ofsubstrates 8 on and off the double substrate handler 26. In addition, apre-conditioning unit 18 is integrated in to the lower stage 16 of thedouble substrate handler 26. The handler is moveable upwardly anddownwardly in directions indicated by arrow H so that it can be alignedwith the substrate exposure table 6.

Referring to FIG. 6, there is shown a substrate handler 28, according tofurther embodiment of the present invention. The substrate handler 8 ismoveable upwardly and downwardly in directions indicated by arrow Jrelative to the substrate exposure table 6. The substrate handler 28 hasan upper stage 14, and lower stage 16 with an integratedpre-conditioning unit 18. The substrate handler 28 is shown locatedadjacent the exposure table 6, and a robot 10 is shown transferring asubstrate 8 on to the substrate handler 28.

FIG. 7 shows a substrate handler, according to one embodiment of thepresent invention. The substrate handler has an upper stage 14 and lowerstage 16 as before, but the upper stage 14 is used to receive unexposedsubstrates from the robot and load them on to the exposure table 6,whereas the lower stage 14 is designed to unload exposed substrates fromthe exposure table 6 to the robot. The stages 14, 16 are supported ateach corner by guide columns 100 that serve guide the vertical movementof the stages. Each column 100 receives a corresponding projection 100 adefined on the edge of each stage and which is slidably disposed withinthe column. It is to be appreciated that in some cases less than foursuch guide columns can be used. A drive mechanism 102 which can becontained, at least in part, in the guide columns serves to move eachstage to the desired vertical position. The mechanism can be constructedso that the movement of the two stages is mechanically coupled so thatthey move in unison. The drive mechanism can have different transmissionratios between the two stages so that the distance between the stageswill vary with their vertical position relative to the columns.

Each of the stages 14, 16 of the substrate handler of FIG. 7 has aplurality of upstanding pins 101 spaced over its surface. These pins 101are designed to support the substrate above the upper surface of a paneldefining the stage, so as to provide a clearance between the uppersurface of the stage panel and the substrate so as to improve access fora robot end effector. The plane occupied by the tips of the pins, ineffect, becomes the operational surface of the stage. The pins 101 arepivotally connected to the stage so that they can move between theupright position and a stored position, where they are no longerupright. This movement of the pins is used to move the supportedsubstrate laterally during its delivery to or from the exposure table.The pins 101 can be provided with bores and connected to a supply ofnegative pressure so that a partial vacuum is applied to help retain thesubstrate on the stage during transportation. In an alternativearrangement, the pins 101 can be moveable in a linear direction alongthe direction of movement of the substrate (i.e., perpendicular to theaxes of the pins). This movement of the pins is used to move thesupported substrate laterally during its delivery to or removal from theexposure table.

In various examples, the stages 14, 16 have a plurality of nozzles (notshown) distributed over the support surface or platform for directing ajet of gas such as air towards the substrate. The nozzles are connectedto a source of such gas and are designed to create a film or cushion ofgas between the upper surface of the stage 14, 16 and the substrate, thefilm or cushion serving to prevent contact of the substrate with thestage surface. Such nozzles can be provided with or without the pins 101described above and can include the facility to control the direction ofthe gas flow so that the substrate can be urged in a predetermineddirection during loading or unloading.

In FIGS. 8 and 8A there is shown a single stage of an alternativesubstrate handler, according to one embodiment of the present invention.The surface of the stage has a plurality of grooves 103 parallel to thedirection of transportation of the substrate. These grooves 103 serve asguides for fingers 104 (see FIG. 8 a) that hold the substrate duringtransportation thereof. The fingers are connected to a transportationbar 105 that extends across the stage surface in a directionperpendicular to the direction of movement. The transportation bar isdriven by a drive member (e.g., a motor) via a transmission element(e.g., a cable, chain or a belt drive) disposed in a housing 106 on eachside of the stage. The surface of the stage has a plurality of nozzles107 that direct a jet of gas, for example air, towards the substrate asdescribed above.

The various embodiments of the substrate handlers described herein canbe optionally fitted with a preconditioning unit that is designed tobring the substrate to the appropriate temperature for exposure. Thiscan be achieved by controlling the temperature of the substrate supportstage by any suitable form of heat-exchanging apparatus. One proposedembodiment is to provide one or more internal or external channels inthe stage and supplying them with temperature controlled water or otherfluid. The substrate can be directly in contact with the surface of thestage or can be supported on an operational surface provided by an airfilm or cushion as described above. In the latter case the air betweenthe support stage and the substrate serves as the heat conductive layeras well as a means for transporting the substrate to or from theexposure stage. The thickness of the air film or cushion whentransporting the substrate is typically in the region of 300 μm and canbe reduced to less than 100 μm when serving to thermally condition thesubstrate.

Referring to FIG. 9, there is shown a “Front in, Front out”loading/unloading sequence of substrates 8, according to one embodimentof the present invention. The loading is to and from the substrateexposure table 6, so-called because a substrate 8 is loaded and unloadedfrom the front of the exposure table 6 (i.e., on the left hand side of ascanner 30 in FIG. 9). This is carried out using the double substratehandler 12. In the Figure, substrates (1), (2) and (3) are shown atvarious positions on the apparatus. At stage (a), the substrate table 6is shown in a starting position supporting an unexposed substrate (2)underneath a scanner 30. The table 6 moves in a direction indicated byarrow L along a base plate BP and underneath the scanner 30, therebyirradiating the substrate (2). Previously exposed substrate (1), is nowunloaded by a robot (not shown) from the upper stage 14 of the doublehandler 12, in a direction indicated as arrow K, i.e., opposite to thedirection of movement of the table 6.

At stage (b), the table continues to move in a direction shown as arrowP, such that substrate (2) continues to be scanned. The substratehandler 12 is moved upwardly in a direction as shown by arrow N, andunexposed substrate (3) is loaded by a robot (not shown) on to the lowerstage 16 of the substrate handler 12. At stage (c), the table 6 is shownin its most extreme position at one end of base plate BP, such that theentire surface of the substrate (2) has been completely scanned. Thismakes sufficient room for the substrate handler 12 to be lowered down ina direction as indicated by arrow Q to the scanning level. At stage (d),substrate (2) is removed off the table 6 in a direction shown by arrow Ron to the upper stage 14 of the substrate handler 12.

At stage (e), the substrate handler 12 is moved upwardly in a directionshown by arrow S so that the lower stage 16 is in horizontal alignmentwith the table 6. Substrate (3) is then moved off the substrate handler12 and on to the table 6 in a direction shown by arrow T. At stage (f),the substrate handler 12 is raised further in a direction shown by arrowU allowing sufficient clearance from the table 6 such that the table 6can be moved back in a direction of arrow X until it has returned to its‘start’ position, as shown at stage (g). At stage (h), the exposuretable 6 is shown moving in a direction shown by arrow Y, such thatsubstrate (3) undergoes the scanning process as described above.Substrate (2) is removed from the substrate handler 12 in a directionshown by arrow W, and the entire sequence is then repeated.

FIG. 10 shows a sequence for loading and unloading substrates 8 to andfrom the substrate exposure table 6 using a double substrate handler 12in which the preconditioning unit is associated with the upper stage 14,according to one embodiment of the present invention.

Referring to FIGS. 11 and 12, there is shown a “Front in, Rear out”sequence of loading/unloading substrates 8 to and from the substrateexposure table 6 using a substrate handler 12, according to variousembodiments of the present invention. One of the stages of the substratehandler 12 has been moved from the front side of the table 6 to the rearside.

FIG. 11 illustrates the concept of “Front in, Rear out”loading/unloading sequence, so-called because a substrate 8 is loaded onto the front of the exposure table 6 (i.e., on the left hand side of thescanner 30 in FIG. 8), and unloaded from the rear of the exposure table6 (i.e., on the right hand side of the scanner in FIG. 8). The apparatusincludes an exposure table 6 on which substrates are supported duringthe scanning procedure by the optic scanner 30. On the loading side 40of the scanner 30, there is provided a pre-conditioner/load plate 32. Onthe opposite unloading side 42 of the scanner 30, there is provided anunload plate 34.

Referring to FIG. 12, at stage (a), a substrate 8 a is shown supportedon the exposure table 6, which is in its ‘start’ position. As table 6moves in a direction indicated by arrow A relative to the scanner 30,substrate 8 a is scanned. A new unexposed substrate 8 b is then loweredinto position on the pre-conditioner/load plate 32 by a robot (notshown). At stage (b), once the table has reached its ‘end’ position atone extremity of a base plate BP, scanning of the substrate 8 a has beencompleted. The unload plate 34 is then moved downwardly in a directionshown by arrow B until it is in horizontal alignment with the table 6.At stage (c), the scanned substrate 8 a is then moved in a directionshown by arrow C on to the unload plate 34. At stage (d), the unloadplate 34 is moved upwardly to allow sufficient clearance for the table 6to pass thereunder as it moves in a direction shown by arrow D back toits ‘start’ position.

At stage (e), the pre-conditioner/load plate 32 loaded with theunscanned substrate 8 b is lowered until it is in horizontal alignmentwith the table 6. In addition, the scanned substrate 8 a is removed offthe unload plate 34 by a robot (not shown). At stage (f), substrate 8 bis moved across in a direction shown by arrow G off the load plate 32and on to the exposure table 6. At stage (g), the table 6 is moved awayfrom the scanner 30 in a direction indicated by arrow I. Thepre-conditioner load plate 32 is raised in a direction shown by arrow Hto provide clearance for the table 6 to return in a direction shown byarrow J, thereby scanning the substrate 8 b. The entire sequence is thenrepeated.

The apparatus having the double substrate handler 12 allows for anincreased product throughput due to the decreased substrate 8 swappingtime and resultant decreased down-time. The handler that is capable ofhandling two substrates at the same time can swap substrates 8 without“put away and pick up” movements seen in conventional handlers. Inaddition, the substrate handler 12 can be integrated with apre-conditioning unit 18 on the same floor space further increasingthroughput. Furthermore, the pre-conditioning unit 18 can be situatednear the substrate exposure table 6. Hence, no time is lost for thenecessary pre-conditioning of substrates 8.

In the embodiments of FIGS. 11 and 12, the unloader 34 is disposedwithin the footprint of the scanning table 6, such that when the tableis at the right hand extent of its travel (see FIG. 12 g) the unloader 6is positioned directly above the table 6.

FIGS. 13 a and 13 b show another embodiment of the present invention, inwhich the unloader 34 can be disposed beyond footprint of the scanningtable. In this embodiment, the unloader 34 is disposed further to theright of the table 6 than in the previous embodiment. When a substrate 8is being exposed the both parts 32, 34 of the handler are raisedvertically above the level of the table, as shown in FIG. 13 a. Thehandler is lowered to perform the loading and unloading operations andthe arrangement is such that when the exposure table 6 is at the limitof its travel to the right (see FIG. 13 b) the unloader 34 is stillclear of its footprint and so the exposed substrate can be unloadeddirectly as shown. The exposure table 6 travels over a base member thatcan be in the form of a plate and which is not shown in FIG. 13. As canbe seen from FIG. 13 b the arrangement allows simultaneous loading andunloading of the substrates 8. Thus, although this configurationincreases the overall footprint of the apparatus, it does provide for animprove throughput as the transport time to and from the table isreduced.

Referring to FIGS. 14 a, b, and c, there are shown comparative plan andside views of a conventional lithographic apparatus (FIG. 14 a), and twoembodiments of the apparatus according to the present invention (FIGS.14 b and 14 c). FIGS. 14 a-14 c show the apparatus consisting of ahandling stage 36, an exposure tool 38, and an optic scanner 30 (visiblein the side view). These parts of the apparatus are contained with aframe 50 structure made up of a series of cover plates 52.

In the conventional apparatus shown in FIG. 14 a, the handling stage islocated adjacent to the exposure tool 38. In addition, thepre-conditioning stage for the substrate 8 is also situated next to theexposure table 6. Because a pre-conditioning stage is at least the samesize as the substrate 8, this is a significant amount of the apparatus‘footprint,’ i.e., the total surface area of the apparatus.

In the embodiment shown in FIG. 14 b, showing the apparatus using the“Front in, Front out” loading/unloading system, for example asillustrated in FIG. 7, the handling stage 36 is positioned above and toone side of the exposure tool 38. In the embodiment showing in FIG. 14c, the apparatus uses the “Front in, Rear out” loading/unloading system,for example as illustrated in FIGS. 8 and 9, in which the apparatus hastwo handling stages 36, one either side of the scanner 30, all of whichare located above the exposure tool. Hence, it will be appreciated thatthe ‘footprint’ of the two embodiments of the apparatus according to thepresent invention (i.e., FIGS. 14 b & 14 c), is much less than that ofthe conventional apparatus, because the handling stage(s) 36 ispositioned above the exposure tool 38 as opposed to being positionedadjacent the exposure tool 38. This is a footprint reduction ofapproximately 30%.

Referring to FIGS. 15 a and 15 b, there is shown the configuration ofthe apparatus during exposure of a substrate 8 (FIG. 15 a), and duringsubstrate exchange via a handling stage (FIG. 15 b), according to oneembodiment of the present invention. The apparatus has a side wall 44from which the handling stage 36 is supported via rollers 46. Therollers 46 allow vertical movement along the side wall 44. It will beappreciated that the handling stage 36 is positioned above the exposuretool 38 at all times thereby reducing the footprint of the apparatus.During substrate 8 exposure, the table 6 is moved horizontally from sideto side underneath the exposure scanner 30. The table 6 is also providedwith rollers 48 to allow movement along the exposure tool 38. The robot10, which is located outside of the apparatus footprint, is showntransferring a substrate 8 on to the handling stage 36.

As shown in FIG. 15 b, during substrate 8 exchange, the handling stage36 is lowered in a direction indicated by arrow K, until it is inhorizontal alignment with the exposure table 6, and hence, substrate 8which has just been exposed. The substrate 8 is then moved in adirection illustrated by arrow L between the handling stage 36 and theexposure table 6.

Referring to FIG. 16 a, there is shown a similar apparatus to that shownin FIG. 15, except that a double handling pre-conditioning stage isused, i.e., a double substrate handler 12, for example as discussed withreference to FIG. 9. The substrate handler 12 can hold a substrate 8 onthe upper and also lower stages 14,16. The substrate handler 12 can movevertically up and down the side wall 44 by means of the rollers 46. Inaddition, the exposure table 6 moves left and right underneath thescanner 30. It will be appreciated that the substrate handler 12 isusually above the exposure tool 38, thereby reducing the footprint ofthe apparatus.

Referring to FIG. 16 b, there is shown substrate 8 exchange, for exampleusing the apparatus discussed with reference to FIGS. 11 and 12. Theapparatus has two handling stages 32,34, one on either side of thescanner 30. Each stage 32, 34 is able to move up and down theirrespective side wall 44 along rollers 46. The apparatus has two robots10, one which loads substrates 8 on to the loading stage 32 on the frontside, and one which unloads substrates 8 from the unload stage 34 on therear side.

In one example, the significantly smaller apparatus footprint (30%reduction), and integrated pre-conditioning unit 18. There is aresultant lower machine cost because of the smaller machine footprintand volume. Also, the total weight of the machine is less due to thesmaller footprint. Also, the apparatus is compatible with the doublesubstrate loading configuration with the double handler 12.

Referring to FIGS. 17 a, 17 b, 17 c, and 17 d, there is shown analternative embodiment of a double handler/pre-conditioner 54. In thisembodiment, the upper stage 14 and the lower stage 16 are pivotable withrespect to each other such that the distance therebetween can be varied,i.e., increased or decreased. Hence, if a substrate 8 is being loaded orunloaded from the handler 54, the distance between the upper and lowerstages 14,16 of the handler can be increased so that access thereto, forexample, by a robot 10, is easier. If the handler 54 is being movedwithin the apparatus, for example, vertically upwardly or downwardlywith respect to the scanner 30, then the distance between the upper andlower stages 14,16 of the handler 54 can be decreased to minimize thevolume it occupies and to bring a pre-conditioning unit (not shown inthis embodiment) closer to the appropriate stage and substrate.

The handler 54 comprises a collapsible frame with two mutually opposingelongate base portions 58. A short spacer portion in the form of a leg56 is pivotally attached to each end of the two base portions 58 by ahinge 60 and extends perpendicularly away therefrom. The upper stage 14of the handler 54 is pivotally attached by a hinge 60 to an end of eachof the four legs 56 distal from the base portion 58. The lower stage 16is pivotally attached by a hinge 60 to midway along each of the fourlegs 56. Hence, the upper and lower stages 14,16 are able to pivot abouthinges 60 on the spacer portions 56, thereby moving from a fully openconfiguration as illustrated in FIGS. 17 a and 17 b, to a partially openconfiguration shown in FIG. 17 c, to a closed or locked position shownin FIG. 17 d. Collapsing of the stages 14,16 by pivoting the legs 56 canbe effected by any kind of suitable actuator such as, for example, oneor more hydraulic or pneumatic rams that are operable under the controlof a computer.

In an alternative arrangement, legs 56 can be configured to be axiallyextendable and retractable (this may be achieved, for example,hydraulically or pneumatically), rather than pivotable.

In one example, the manner in which the pivotable handler 54 is able toopen and close, thereby facilitating access to the substrates 8 when thehandler 54 is in the open configuration as illustrated in FIG. 17 b, and‘lock’ substrates in the lower stage 16 when in the closed configurationas illustrated in FIG. 17 d.

FIGS. 18 a, 18 b, and 18 c show three different versions of substratehandlers that are configured to support more than one substrate at atime, according to various embodiments of the present invention. In FIG.18 a there is shown a substrate handler 12 adjacent to an exposure table6. A robot (not shown) is used to load the handler with two adjacentunexposed substrates N1, N2. These two substrates N1 and N2 can then beloaded simultaneously on to the substrate table 6 to the positionsindicated by reference numbers E1 and E2. FIG. 18 b illustrates oneembodiment in which four substrates N1-N4 arranged into a 2 by 2 matrixcan be loaded simultaneously to positions E1 to E4 and FIG. 18 c shows aversion whereby three substrates N1 to N3 arranged in parallel areloaded simultaneously. The same arrangement can be used to unloadmultiple exposed substrates simultaneously. It will be appreciated thatthe substrate handlers can have the same design as any of thosedescribed above.

FIG. 19 illustrates an alternative embodiment of the substrate handler,according to one embodiment of the present invention. The substrate 8 issupported above the surface 200 of the platform 201 by means of pins 202that are vertically movable (in the direction of the arrows) in holes203 in the platform 201 by any suitable actuator. Although not shown inthis figure the tops of the pins can be fitted with rollers of the kindshown in FIG. 2 or 5. It is to be understood that the platform couldalso be the preconditioning unit referred to above.

CONCLUSION

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be apparent to persons skilledin the relevant art that various changes in form and detail can be madetherein without departing from the spirit and scope of the presentinvention. Thus, the breadth and scope of the present invention shouldnot be limited by any of the above-described exemplary embodiments, butshould be defined only in accordance with the following claims and theirequivalents.

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections can set forth one or more,but not all exemplary embodiments of the present invention ascontemplated by the inventor(s), and thus, are not intended to limit thepresent invention and the appended claims in any way.

1. A substrate handler, comprising: a support surface configured tocarry a substrate; and a pre-conditioning unit configured topre-condition the substrate; wherein the substrate handler is configuredto move the substrate relative to a substrate table.
 2. The substratehandler of claim 1, wherein: the pre-conditioning unit comprises adevice configured to control a temperature of the substrate; and thedevice comprises a heat-exchanging element configured to transfer heataway from or to the substrate.
 3. The substrate handler of claim 2,wherein: the heat-exchanging element comprises a heat exchanging platearranged to be in thermal contact with the substrate duringpre-conditioning; and the heat exchanging plate comprises at least onechannel extending therealong, which heat exchanging plate is configuredto heat or cool the substrate by thermal conduction.
 4. The substratehandler of claim 2, wherein: the pre-conditioning unit comprises fluidarranged to flow along the at least one channel, whereby heat isconducted to or away from the substrate; and the substrate handler isconfigured to maintain the fluid at a substantially constanttemperature.
 5. The substrate handler of claim 1, wherein: thepre-conditioning unit is configured to generate an air film between theplate and the substrate during pre-conditioning; and the air film servesto transfer heat to or from the substrate.
 6. The substrate handler ofclaim 1, wherein the pre-conditioning unit is one of integrated with ordisposed substantially adjacent the substrate handler.
 7. A lithographicapparatus, comprising: a base plate; a substrate table configured tosupport a substrate, wherein the base plate is configured to support thesubstrate table; a patterning system configured to provide a pattern toa target portion of the substrate; and a substrate handler configured tomove the substrate relative to the substrate table, the substratehandler being positioned substantially over the base plate.
 8. Thelithographic apparatus of claim 7, further comprising a guide memberconfigured to support a substrate support surface of the substratehandler.
 9. The lithographic apparatus of claim 8, wherein: thesubstrate support surface is supported on the guide member via at leastone guide element that is configured to permit movement in a directionperpendicular to a plane of the substrate table, in use, the guideelement is configured to allow the support surface to move vertically upand down the guide member.
 10. The lithographic apparatus of claim 9,wherein the guide element comprises at least one of a roller, a bush, aball bush, or air bearings.
 11. A method comprising: moving a substratehandler so that a first support surface is substantially aligned in ahorizontal plane with a substrate table; loading a substrate directlyfrom the first support surface of the substrate handler onto thesubstrate table; patterning a substrate using the patterning system;unloading the exposed substrate from the substrate table onto a secondsupport surface of the substrate handler; and removing the exposedsubstrate from the second support surface of the substrate handler. 12.The method of claim 11, wherein: the first support surface of thesubstrate handler is substantially aligned in the horizontal plane withthe substrate table prior to placing the substrate thereupon; and thesecond support surface of the substrate handler is substantially alignedin the horizontal plane with the substrate table previous to the exposedsubstrate being moved thereupon.
 13. The method of claim 11, wherein theloading is performed on one side of the patterning system and theunloading is performed substantially simultaneously on the opposite sideof the patterning system.
 14. A method, comprising: receiving asubstrate on a substrate table supported by a base plate; patterning atarget portion of the substrate; and moving the substrate relative tothe substrate table using a substrate handler, the substrate handlerbeing positioned substantially over the base plate.
 15. The method ofclaim 14, wherein the substrate handler is moved in a verticaldirection.
 16. The method of claim 14, wherein the substrate table movesrelative to the base plate during scanning.
 17. A lithographicapparatus, comprising: a substrate table configured to support asubstrate, the substrate table being supported on a base plate andtraveling therealong during a scanning operation between a startposition and an end position; a patterning system configured to providea pattern to a target portion of the substrate, and a substrate handlerconfigured to move the substrate relative to the substrate table, thesubstrate handler comprising, a loading platform disposed on one side ofthe substrate table above the base plate, and an unloading platformdisposed on an opposite side of the substrate table and to one side ofthe base plate, at least the loading platform being vertically movablebetween a raised position above the substrate table and a loweredposition in which the unloading platform is substantially aligned in ahorizontal plane with the substrate table, wherein the loading platformis configured to: load the substrate onto the table if the loadingplatform is in the lowered position, and receive the substrate from thesubstrate table if the loading platform is at an end position after thescanning operation, wherein both the loading and the unloading platformare substantially level with the substrate table when the substratetable is at the end position so that loading and unloading is configuredto be performed substantially simultaneously.
 18. A substrate handler,comprising: a substrate table configured to support a substrate duringexposure to a beam of radiation; and a plurality of platforms, whereineach platform is configured to carry the substrate, wherein thesubstrate handler is configured to: load the substrate onto thesubstrate table before exposure, and unload the substrate from thesubstrate table after exposure.
 19. The substrate handler of claim 18,wherein a platform of the plurality of platform is configured to carrytwo or more substrates.